Do not enable LLD by default in the dist profile

History of us building & shipping LLD for `dist` builds:
1) We used to unconditionally build & ship LLD in bootstrap
2) This was causing problems for people doing custom `dist` builds (https://rust-lang.zulipchat.com/#narrow/stream/326414-t-infra.2Fbootstrap/topic/MSVC.20Runtime.20mismatch.20when.20building.20LLD)
3) #126701 made shipping of LLD optional, but to preserve previous behavior, it forcefully enabled `rust.lld = true` in the `dist` profile by default, and overwrote the default to `false` on our CI for external LLVM builds.
    - This also didn't match the documentation of `rust.lld` in `bootstrap.example.toml`, which I previously missed.
4) However, since the external LLVM opt-out was only implemented for our CI, and not for all `dist` users, this started causing issues for people `dist`ing with external LLVM (#143076). The problem is that the default shouldn't be "true", but "LLD is enabled when LLVM isn't external", but this is not possible to do only in TOML.

So this PR reverses the behavior. LLD is not enabled by default in `dist` anymore. We switch our CI to *opt into* disting LLD, unless an external LLVM is used. External `dist` users can still opt into enabling LLD, but if they do so while also using external LLVM, they will now get a [hard error](#143175).

r? `@jieyouxu`

try-job: x86_64-mingw
try-job: dist-x86_64-linux

Do not enable LLD by default in the dist profile

History of us building & shipping LLD for `dist` builds:
1) We used to unconditionally build & ship LLD in bootstrap
2) This was causing problems for people doing custom `dist` builds (https://rust-lang.zulipchat.com/#narrow/stream/326414-t-infra.2Fbootstrap/topic/MSVC.20Runtime.20mismatch.20when.20building.20LLD)
3) #126701 made shipping of LLD optional, but to preserve previous behavior, it forcefully enabled `rust.lld = true` in the `dist` profile by default, and overwrote the default to `false` on our CI for external LLVM builds.
    - This also didn't match the documentation of `rust.lld` in `bootstrap.example.toml`, which I previously missed.
4) However, since the external LLVM opt-out was only implemented for our CI, and not for all `dist` users, this started causing issues for people `dist`ing with external LLVM (#143076). The problem is that the default shouldn't be "true", but "LLD is enabled when LLVM isn't external", but this is not possible to do only in TOML.

So this PR reverses the behavior. LLD is not enabled by default in `dist` anymore. We switch our CI to *opt into* disting LLD, unless an external LLVM is used. External `dist` users can still opt into enabling LLD, but if they do so while also using external LLVM, they will now get a [hard error](#143175).

r? `@jieyouxu`

try-job: `x86_64-mingw*`
try-job: dist-x86_64-linux

Rollup of 9 pull requests

Successful merges:

 - #143019 (Ensure -V --verbose processes both codegen_backend and codegen-backend)
 - #143140 (give Pointer::into_parts a more scary name and offer a safer alternative)
 - #143175 (Make combining LLD with external LLVM config a hard error)
 - #143180 (Use `tracing-forest` instead of `tracing-tree` for bootstrap tracing)
 - #143223 (Improve macro stats printing)
 - #143228 (Handle build scripts better in `-Zmacro-stats` output.)
 - #143229 ([COMPILETEST-UNTANGLE 1/N] Move some some early config checks to the lib and move the compiletest binary)
 - #143246 (Subtree update of `rust-analyzer`)
 - #143248 (Update books)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup merge of #143175 - Kobzol:bootstrap-lld-external-llvm-config, r=Jieyouxu

Make combining LLD with external LLVM config a hard error

Younger me made this only a warning in #139853, because our post-dist tests were relying on this. But that was not a good idea, because there are a bunch of places in bootstrap that outright try to build LLD/copy LLD to sysroot when `lld_enabled` is true (rightfully so), which is causing issues (#143076). Instead of piling more hacks, I'd like to just disallow this, and if we need to use a hack, do it only for our CI.

If this breaks the CI post-dist tests, I'll either add some special environment variable for it, or, as an alternative, make the error back into a warning, but also disable `lld_enabled` when this situation happens.

try-job: dist-x86_64-linux

Fixes: #143175

…r=Jieyouxu

Make combining LLD with external LLVM config a hard error

Younger me made this only a warning in rust-lang/rust#139853, because our post-dist tests were relying on this. But that was not a good idea, because there are a bunch of places in bootstrap that outright try to build LLD/copy LLD to sysroot when `lld_enabled` is true (rightfully so), which is causing issues (rust-lang/rust#143076). Instead of piling more hacks, I'd like to just disallow this, and if we need to use a hack, do it only for our CI.

If this breaks the CI post-dist tests, I'll either add some special environment variable for it, or, as an alternative, make the error back into a warning, but also disable `lld_enabled` when this situation happens.

try-job: dist-x86_64-linux

Fixes: rust-lang/rust#143175

…ieyouxu

Do not enable LLD by default in the dist profile

History of us building & shipping LLD for `dist` builds:
1) We used to unconditionally build & ship LLD in bootstrap
2) This was causing problems for people doing custom `dist` builds (https://rust-lang.zulipchat.com/#narrow/stream/326414-t-infra.2Fbootstrap/topic/MSVC.20Runtime.20mismatch.20when.20building.20LLD)
3) rust-lang#126701 made shipping of LLD optional, but to preserve previous behavior, it forcefully enabled `rust.lld = true` in the `dist` profile by default, and overwrote the default to `false` on our CI for external LLVM builds.
    - This also didn't match the documentation of `rust.lld` in `bootstrap.example.toml`, which I previously missed.
4) However, since the external LLVM opt-out was only implemented for our CI, and not for all `dist` users, this started causing issues for people `dist`ing with external LLVM (rust-lang#143076). The problem is that the default shouldn't be "true", but "LLD is enabled when LLVM isn't external", but this is not possible to do only in TOML.

So this PR reverses the behavior. LLD is not enabled by default in `dist` anymore. We switch our CI to *opt into* disting LLD, unless an external LLVM is used. External `dist` users can still opt into enabling LLD, but if they do so while also using external LLVM, they will now get a [hard error](rust-lang#143175).

r? `@jieyouxu`

try-job: `x86_64-mingw*`
try-job: dist-x86_64-linux

Rollup merge of #143255 - Kobzol:disable-lld-by-default, r=jieyouxu

Do not enable LLD by default in the dist profile

History of us building & shipping LLD for `dist` builds:
1) We used to unconditionally build & ship LLD in bootstrap
2) This was causing problems for people doing custom `dist` builds (https://rust-lang.zulipchat.com/#narrow/stream/326414-t-infra.2Fbootstrap/topic/MSVC.20Runtime.20mismatch.20when.20building.20LLD)
3) #126701 made shipping of LLD optional, but to preserve previous behavior, it forcefully enabled `rust.lld = true` in the `dist` profile by default, and overwrote the default to `false` on our CI for external LLVM builds.
    - This also didn't match the documentation of `rust.lld` in `bootstrap.example.toml`, which I previously missed.
4) However, since the external LLVM opt-out was only implemented for our CI, and not for all `dist` users, this started causing issues for people `dist`ing with external LLVM (#143076). The problem is that the default shouldn't be "true", but "LLD is enabled when LLVM isn't external", but this is not possible to do only in TOML.

So this PR reverses the behavior. LLD is not enabled by default in `dist` anymore. We switch our CI to *opt into* disting LLD, unless an external LLVM is used. External `dist` users can still opt into enabling LLD, but if they do so while also using external LLVM, they will now get a [hard error](#143175).

r? `@jieyouxu`

try-job: `x86_64-mingw*`
try-job: dist-x86_64-linux

…r=Jieyouxu

Make combining LLD with external LLVM config a hard error

Younger me made this only a warning in rust-lang/rust#139853, because our post-dist tests were relying on this. But that was not a good idea, because there are a bunch of places in bootstrap that outright try to build LLD/copy LLD to sysroot when `lld_enabled` is true (rightfully so), which is causing issues (rust-lang/rust#143076). Instead of piling more hacks, I'd like to just disallow this, and if we need to use a hack, do it only for our CI.

If this breaks the CI post-dist tests, I'll either add some special environment variable for it, or, as an alternative, make the error back into a warning, but also disable `lld_enabled` when this situation happens.

try-job: dist-x86_64-linux

Fixes: rust-lang/rust#143175